Propeller brake



Feb. 14, 1961 R. G. LARKIN ETAL 2,971,613

PROPELLER BRAKE Filed April 19, 1957 5 Sheets-Sheet 1 /g 4 /Z /V 1 m Y974 Tram/:Y

Feb. 14, 1961 R. G. LARKIN ErAL PROPELLER BRAKE 3 Sheets-Sheet 2 FiledApril 19, 1957 @MR Ek f I vll from/Er Feb. 14, 1961 R. G.1 ARK1N ErAl.2,971,613

PROPELLER BRAKE Filed April 19, 1957 5 SheeiLs-Sheet 3 2,971,613PROPELLER BRAKE Robert G. Larkin, Victor W. Peterson, and Herbert H.

Schnepel, Indianapolis, Ind., assignors to G eneral Motors Corporation,Detroit, Mich., a corporation of Delaware Filed Apr. 19, 1957, Ser. No.653,885 Claims. (Cl. 18S-110) This invention relates to brakes and moreparticularly to a brake for an aircraft propeller. This invention isparticularly applicable to brakes for propellers driven either by pistontype or gas turbine engines in arrangements wherein either a singleengine or a plurality of engines drive either a single propeller or morethan one propeller. The principles of the invention may be applied tobraking power elements in other fields than the field of aircraftpropulsion.

When aircraft engines are inoperative it is often desirable to apply abrake to hold the propeller from rotation in either directon. It isnecessary that the brake be released upon engine starting and that thebrake act to absolutely prevent reverse rotation of the propeller duringight, and further that the brake be prevented from being applied duringperiods of operation wherein applications of the brake would be harmfulto the engine, propeller or the brake itself. It is important that thebrake be applied only when the propeller is rotating at low speeds inorder to minimize brake wear and yet lto ensure that the brake isapplied with suicient force to perform its function without undueslipping.

Various types of brakes have been utilized which conform to theserequirements, such brakes being shown in the applications of Victor W.Peterson, S.N. 231,465, filed lune 14, 1951, now Patent No. 2,826,255,and S.N. 313,960, tiled October 9, 1952, now Patent No. 2,860,713. Thepropeller brakes shown in the Peterson applications utilize cone brakesthat are spring applied, and pressure released and have self-energizinghelical splines to apply the brake upon tendency for reverse propelleroperation.

The present invention is an improvement on the brakes of theabove-mentioned applications and provides in a relatively simplestructure a brake that satises the conditions set forth above. The brakeutilizes a spiral brake band that is wound on a brake drum to hold thepropeller from rotation in either direction and is self-energizing tohold the brake drum and propeller from reverse rotation.

The invention is described herein in terms of the preferred embodimentin an aircraft power plant comprising an engine with power transmissionto a variable pitch propeller. The power plant is provided with a brakewhich prevents rotation of the propeller while the engine isinoperative.

It is therefore an object of the invention to provide an improved powerplant, particularly one of the turboprop type, to provide an improvedbraking arrangement for the power plant and to provide an improvedbraking control particularly suited for the type of applicationdescribed above.

Briey, the invention in its preferred embodiment comprises a brake drumconnected to the member to be braked, in this case a shaftgear-connected to the aircraft propeller. A spiral brake band having oneend fixed to a stationary member and the other end having gear teethformed thereon surrounds the brake drum. A rack'in 2,971,613 PatentedFeb. 14, 19671 ice engagement with the teeth on the brake band is movedby a control spring to wrap the band on the drum foi' braking the same.Engine operation responsive fluid pressure acts to move the rack in aband unwinding direction. The band applying spring force is controlledso as to be alternatively effective or ineifective to move the rack in aband winding direction.

Further objects and advantages of the present inven-v tion willbeapparent from the following description, reference being had to theaccompanying drawings wherein a preferred form of the present inventionis clearly shown.

Figure l illustrates the aircraft power plant in which the preferredembodiment of the invention is utilized.

Figure 2 is a sectional view of the brake mechanism located in the powertransmission unit of the power plant.

Figure 3 is an enlarged view showing the brake operating mechanism andcontrol.

Figure 4 is an enlarged View similar to Figure 2 with a portion of theligure broken away.

Figure 5 is a view showing an alternative control arf rangement for thebrake. g

Referring now to the drawings in detail and more particularly to Figure1, a gas turbine engine generally designated by A is connected to drivea reduction gear assembly B which in turn drives a variable pitchpropeller C. The engine A comprises an air inlet section 10, acompressor section 11, combustion chamber area 12, a. turbine sectioni3, and an exhaust duct 14. The engine may include one or more turbines,at least one of which is connected to drive an engine output shaft 15which extends into the reduction gear assembly B.

Referring now to Figure 2, which shows a portion of the gear assembly B,the gear input shaft 15 is either directly connected to an annular drivemember 17 or indirectly through an overrunning clutch (not shown). Theannular member i7 is splined to a pinion drive shaft 19 having xedthereon a pinion gear 21 adapted to drive a bull gear 22 in turnconnected to other reduction gearing, not shown, to drive the propellerC. The pinion shaft 19 is journalled at one end by a roller bearing 23in a fixed portion of the reduction gear case and at the other end by abearing not shown.

Surrounding the annular member 17, which also serves as a brake drum, isa left hand spiral band 39 having on its internal surface a frictionbrake lining 41. The left end, as viewed in the figures, of the spiralband is connected by means of a spline 43 to a stationary clutch andbrake housing 45 which is a fixed part of the gear box assembly B. Theother or right end of the spiral band 39 is integral with a ring 46which has teeth 47 formed around a portion of its circumference. Asshown in Figures 2, 3 and 4 the teeth 47 engage teeth 51 of a tubularrack piston 49 slidably mounted in a housing 53 carried by a stationaryportion of the gear case. Inside of the tubular rack piston 49 isslidably mounted a control plunger 55 having an enlarged flange portion57 near one end thereof. The flange serves as a guide for reciprocationof the plunger 5S within the rack piston 49 and as a seat for a coilspring 59 which surrounds the major portion of the plunger 55 and whichbears against one end of the rack piston 49. The rack piston 49 has onone end thereof an enlarged piston portion 61 that is slidably receivedin a cylinder 62 carried by the housing 53. The piston 61 and cylinder62 form a chamber 63. A uid line 65 hereinafter referred to as a brakerelease passage is connected into the chamber 63.

The means for controlling the operation of the rack 49 includes acontrolled source 67 of air under pressure including a suitable valvethat is adapted to supply air alternatively to conduit 69 or conduit S4.The conduit 69 conducts air to act on a piston 71 reciprocably mounted 3in a cylinder 73 carried by the stationary gear ease. The piston 71 hasa piston rod 74 extending through a bearing 75 carried by the'cylinder73 and has formed on its end a'cam member 76. As seen in .Figure 3, thecam 76 is located between a roller 77 iixed to the cylinder housing 72and a roller 79 rotatably carried by an element 8d ythat bears againstthe rack control plunger 55. The element Si) is mounted forreciprocation normal to the movement of the piston 71 and cam '76 in aguide '52.

With the elements positioned as shown in Figure 3, the spring 59 actsbetween plunger ange 57 and the piston rack 49 to move the plunger 55 tothe left until restricted byY a snap-ring SI1 carried by the plunger 55,the snapring 81 bearing against the piston rack 49, With the plungershown in this position the spring exerts no force on Ythe piston rack49, the spring force being transmitted to plunger 5S by the snap-ring81. With no force applied to the rack 49, the spiral band 39 is in itsunwrapped or non-braking position.

A port l83 inthe cylinder 73 is connected by conduit 84 to thecontrolled air source 67. When air is supplied through conduit 84 andport 83 into the cylinder 73 above the piston 71, the piston is moveddownto the position shown in Figure 3, wherein the cam 76 allows Ytheroller 79 to be moved to the left by the Vspring 59 to the positionshown. The mechanism which provides for releasing the brake Yduringengine operation includes a pressure pump P connected to lthe `propellerso as to be driven whenever the propeller is rotating. conduit 85leading to a iilter and valve assembly F. The ilter, which may be ofknown type, acts to iilter out undesirable material from the duidsupplied by pump P and allows the uid to pass into a chamber 87. In theevent Ythat the iilter becomes clogged, a by-pass valve S9 is providedwhich will allow passage of iluid from the vpump P around theiilter.Fluid under pressure in chamb'er 37 forces open a check valve 91whereupon it flows into a lubrication and brake release supply chamber93. Leading from the chamber 93 are a plurality of passages v95 'thatlead to various points in the reduction gear for lubrication thereof.The brake release passage 65 leadving into the brake cylinder 62`alsoleads from the chamber 93.V A restricting valve 97 acted on -by aspring 99 acts to cut off supply of uid under pressure to thelubricating passages 95 whenever the pressure in chamber 93 'is below aiixed amount. The restricting valve '97 and the check valve 91 cooperateto maintain a minimum pressure in chamber 93 whenever the 'pressure fromthe 'pump P drops below a predetermined level. The operation andfunction of these valves will be more fully described in the statementof the operation of the brake below.

In place of the piston operated cam and roller assem- -bly shown inFigure 3 there is shown in Figure 5 a 'manual control for plunger 55which includes a lever lil-1 pivotally mounted on a stationary portionof the trans- 'ing 72 and a roller 79 rotatably carried by an element8i?V 'mission case and which can be rotated (either directly or ybymeans of suitable linkage, not shown,) to move the rack 49 to wind theband 39 on the brake drum 17.

Operation With the engine stopped and the brake released the mechanismis in the position of Figure 3. Spring 59 is fully expanded and exertsno force on rack 49 to apply the band. To energize the brake, air fromsource 67 is supplied through pipe 69 toY act on piston 74 causing cam76 to force roller 79 and plunger 55 to the right. This compressesspring 59 whose force moves 'pistony rack 49 to the right and winds theband 39 Yaround drum 17. s U The brakercan be released'prior to startingby supplying air from source 67 through pipe 84 to the upper endofpiston 71,? moving cam 76.downvvard,` which releases the compressedspring 59 to move plunger 55 and roller Pump P supplies pressure to aYenvahie 4 79 to the left until Vrestricted by snap-ring 81. With theplunger in this position the `band is allowed to release, moving rack 49to the left since no force is applied to rack piston 49.

if the brake control cam 76 should be inadvertently left in brake onposition when the engine is started, oil pressure from pump P iiow'sthrough' conduit 85, filter F, check valve 91, and conduit 65 intochamber 63 to act on piston 61 to move the rack 49 to the left or brakeoir position, compressing spring 59. Upon engine shutdown, the brakeremains off until the oil pressure in chamber 63 decreases sufficientlyto allow the force of spring 59 to move the rack 49 to the right toapply the brake band.

During starting and shutdown of the/engine, restricting valve 97prevents a major iiow of oil to the lubrication passage 9S, allowingonly a small bleed through restricted passage 96. This is an aditionalsafety feature by which, if the brake is inadvertently left in the onposition during engine starting, the restricting valve 97 causes themain oil pressure in 'chamber 6,3 to increase rapidly and force piston6i and rack i9 to overcome the spring 59 and move the band to releasedposition. Conversely, on engine shutdown, the restricting valvemaintains sufiicient oil pressure in chamber 63 to prevent actuation ofthe brake band until the propeller speed has dropped to a safe lowValue.

if, during Hight the engine should fail and the propeller begin towindmill the propeller is feathered. it may also be decoupled from theengine by suitable means (not shown). When the propeller is feathered,it slows down, and when the speed reaches a low value safe for brakeapplication, .the displacement of pump P becomes vinsuiiicient to holdpiston 6i against the force of spring 59. The brake is thus no longerheld oi. rl`he brake may thenbe applied by spring S9, then or previouslyenergized by piston 71 or lever itil. rthe propellermay be slightlyoverfeathered, soit tends to rotate .reversely, if desired. if thepropeller attempts to reverse rotation, the band 39 will wind itself ondrum 17 with a force about ten times the normal Yforce exerted throughthe control spring 59. This is due to the left hand spiral of the band39.

The modified control shown in Figure-5 operates in the same manner asthat of Figure 3 with the plunger 55 moved directly by controlV leveritil instead of air operated cam 76.

The invention provides an Vimproved brake control apparatus withautomatic safety features that protect the brake mechanism as lwell asthe propeller, transmission land engine. The principles of the inventionmay easily be utilized in other arts than the aircraft propeller driveart through the-'use of ordinary skill.

It will be apparent to those skilled in the art that many modificationsof the system and components may be made within the scope of theinvention which is not to be considered as limited by the detaileddescription of the embodiment shown.

What is claimed is:

1. A brake mechanism for braking a rotatable member including a spiralbrake band spaced from and surrounding said rotatable member, arelatively fixed member spaced from and surrounding said spiral band,one end of the band being vanchored to said ixed member, band controlmeans carried by the other end of said Spiral band for winding orunwinding the sameion said rotatable member for respectively preventingor allowing rotation of said rotatable member, movable operating meansconnected to said band control means for operating'the same, biasingmeans for at times urging said operating means in a band windingdirection, Fluid pressure responsive means for overcoming said biasingmeans to move -said operating means in a Vvband unwinding' direction,and Aadditional means independent ofsaid fluid pressure means connectedto said biasing means ,for rendering it effective or ineffective to urgesaid operating means in a band winding direction. p

2. In a brake mechanism for braking a rotatable member including aspiral band spaced from and surrounding said member, a relatively fixedmember, one end of said spiral member being anchored to said iixedmember, gear teeth on the other end of said spiral member, a gear rackengaging said teeth for winding or unwinding said band on said rotatablemember for preventing or allowing rotation thereof, a spring engagingsaid rack, controllable means for causing said spring to exert a forceon said rack in a band winding direction, a uid responsive pistonconnected to said rack for moving it in a band unwinding directionagainst the force of said spring, and means responsive to rotation ofsaid rotatable member for supplying iluid under pressure to said piston.

3. A brake mechanism for braking a rotatable member including a spiralband spaced from and surrounding said rotatable member, a relatively xedmember spaced from and surrounding said spiral band, one end of saidband being anchored to said xed member, the other end of said spiralband having teeth on the outer periphery, a reciprocable rack engagingsaid teeth arranged to Wind and unwind said band on said rotatablemember for respectively preventing and allowing rotation of saidrotatable member, biasing means engaging said rack, movable meansengaging said biasing means for causing the same to urge the rack in aband winding direction, iluid pressure means operatievly connected tosaid rack for moving the rack against said biasing means in a bandunwinding direction, and uid pressure supply means connected to at timessupply Huid under pressure to said iluid pressure means for causing saiduid pressure means to move said rack against said biasing means in aband unwinding direction.

4. The brake mechanism of claim 3 wherein said movable means has twopositions, a rst position of contact with said biasing means to cause itto exert a force in said rack to move it in a winding direction and asecond position of contact with said biasing means where said biasingmeans exerts substantially zero force on said rack.

5. A brake mechanism for braking a rotatable member including a spiralband spaced from and surrounding said rotatable member, a relativelyiixed member spaced from Iand surrounding said spiral band, one endvofsaid band being anchored to said fixed member, the other end of saidspiral band having teeth on the outer periphery, a reciprocable rackengaging said teeth arranged to wind and unwind said band on saidrotatable member for respectively preventing and allowing rotation ofsaid rotatable member, biasing means engaging said rack, movable meansengaging said biasing means for causing the same to urge the rack in aband winding direction, fluid pressure means operatively connected tosaid rack for moving the rack against said biasing means in a bandunwinding direction, uid pressure supply means responsive to the speedof rotation of said rotatable means and connected I,to supply tluidunder variable pressure to said uid prespredetermined pressure from saidsupply means to allow said biasing means to move said rack in a bandwinding direction. i

1References Cited in the tile of this patent UNITED STATES PATENTS589,779 Hall Sept. 7, 1897 595,732 Pitt Dec. 21, 1897 2,144,423 CaldwellJan. 17, 1939 2,486,672 Notestein et al. Nov. 1, 1949 2,502,898 SpitzerApr. 4, 1950 2,702,100 Montieth Feb. 15, 1955 2,737,018 Bain Mar. 6,1956 2,826,255 Peterson Mar. 11, 1958 UNITED STATES PATENT OFFICECERTIFICATION OF CORRECTION Patent No. 2,971,613 Februarylt'-, 1961Robert G., Larkin et a1.V

tified that error appears in the above numbered patf 1t s hereby eer nand that the said Letters Patent should read as en' requiring Correctieeor''ected below'.

strike out "ing 72 and a roller 79 0"; line 59V after "the" insert sespring 59 to move the n.

Column 3, line 57, rotatably carried by an element 8 plunger 55 to theright to cau Sigean. and sealed this 18x-,h day of July4 1961.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents

